Modelling of Lamb waves in composite laminated plates excited by interdigital transducers

The technique of permanently attaching interdigital transducers (IDT) to either flat or curved structural surfaces to excite single Lamb wave mode has demonstrated great potential for quantitative non-destructive evaluation and smart materials design, In this paper, the acoustic wave field in a composite laminated plate excited by an IDT is investigated. On the basis of discrete layer theory and a multiple integral transform method, an analytical-numerical approach is developed to evaluate the surface velocity response of the plate due to the IDTs excitation. In this approach, the frequency spectrum and wave number spectrum of the output of IDT are obtained directly. The corresponding time domain results are calculated by applying a standard inverse fast Fourier transformation technique. Numerical examples are presented to validate the developed method and show the ability of mode selection and isolation. A new effective way of transfer function estimation and interpretation is presented by considering the input wave number spectrum in addition to the commonly used input frequency spectrum. The new approach enables the simple physical evaluation of the influences of IDT geometrical features such as electrode finger widths and overall dimension and excitation signal properties on the input-output characteristics of IDT. Finally, considering the convenience of Mindlin plate wave theory in numerical computations as well as theoretical analysis, the validity is examined of using this approximate theory to design IDT for the excitation of the first and second anti-symmetric Lamb modes. (C) 2002 Elsevier Science Ltd. All rights reserved.

Development of axon pathways in the zebrafish central nervous system

The zebrafish has a number of distinct advantages as an experimental model in developmental biology. For example, large numbers of embryos can be generated in each lay, development proceeds rapidly through a very precise temporal staging which exhibits minimal batch-to-batch variability, embryos are transparent and imaging of wholemounts negates the need for tedious histological preparation while preserving three-dimensional spatial relationships. The zebrafish nervous system is proving a convenient model for studies of axon guidance because of its small size and highly stereotypical trajectory of axons. Moreover, a simple scaffold of axon tracts and nerves is established early and provides a template for subsequent development. The ease with which this template can be visualized as well as the ability to spatially resolve individual pioneer axons enables the role of specific cell-cell and molecular interactions to be clearly deciphered. We describe here the morphology and development of the earliest axon pathways in the embryonic zebrafish central nervous system and highlight the major questions that remain to be addressed with regard to axon guidance.

Novel composites of TiO2 (anatase) and silicate nanoparticles

Thermally stable composite nanostructures of titanium dioxide (anatase) and silicate nanoparticles were prepared from Laponite clay and a sol of titanium hydrate in the presence of poly(ethylene oxide) (PEO) surfactants. Laponite is a synthetic clay that readily disperses in water and exists as exfoliated silicate layers of about 1-nm thick in transparent dispersions of high pH. The acidic sol solution reacts with the clay platelets and leaches out most of the magnesium in the clay, while the sol particles hydrolyze further due to the high pH of the clay dispersion. As a result, larger precursors of TiO2 nanoparticles form and condense on the fragmentized pieces of the leached silicate. Introducing PEO surfactants into the synthesis can significantly increase the porosity and surface area of the composite solids. The TiO2 exists as anatase nanoparticles that are separated by silicate fragments and voids such that they are accessible to organic molecules. The size of the anatase particle can be tailored by manipulating the experimental parameters at various synthesis stages. Therefore, we can design and engineer composite nanostructures to achieve better performance. The composite solids exhibit superior properties as photocatalysts for the degradation of Rhodamine 6G in aqueous solution.

Visual Biology of Hawaiian Coral Reef Fishes. I. Ocular Transmission and Visual Pigments

The visual biology of Hawaiian reef fishes was explored by examining their eyes for spectral sensitivity of their visual pigments and for transmission of light through the ocular media to the retina. The spectral absorption curves for the visual pigments of 38 species of Hawaiian fish were recorded using microspectrophotometry. The peak absorption wavelength (lambda(max)) of the rods varied from 477-502 nm and the lambda(max) of individual species conformed closely to values for the same species previously reported using a whole retina extraction procedure. The visual pigments of single cone photoreceptors were categorized, dependent on their lambda(max)-values, as ultraviolet (347-376 nm), violet (398-431 nm) or blue (439-498 nm) sensitive cones. Eight species possessed ultraviolet-sensitive cones and 14 species violet-sensitive cones. Thus, 47% of the species examined displayed photosensitivity to the short-wavelength region of the spectrum. Both identical and nonidentical paired and double cones were found with blue sensitivity or green absorption peaks (> 500 nm). Spectrophotometry of the lens, cornea, and humors for 195 species from 49 families found that the spectral composition of the light transmitted to the retina was most often limited by the lens (73% of species examined). Except for two unusual species with humor-limited eyes, Acanthocybium solandri (Scombridae) and the priacanthid fish, Heteropriacanthus cruentatus, the remainder had corneal-limited eyes. The wavelength at which 50% of the light was blocked (T50) was classified according to a system modified from Douglas and McGuigan (1989) as Type I, T50 < = 355 nm, (32 species); Type IIa, 355 < T50 < = 380 nm (30 species); Type IIb, 380 < T50 405 nm (84 species). Possession of UV-transmitting ocular media follows both taxonomic and functional lines and, if the ecology of the species is considered, is correlated with the short-wavelength visual pigments found in the species. Three types of short-wavelength vision in fishes are hypothesized: UV-sensitive, UV-specialized, and violet-specialized. UV-sensitive eyes lack UV blockers (Type I and IIa) and can sense UV light with the secondary absorption peak or beta peak of their longer wavelength visual pigments but do not possess specialized UV receptor cells and, therefore, probably lack UV hue discrimination. UV-specialized eyes allow transmission of UV light to the retina (Type I and IIa) and also possess UV-sensitive cone receptors with peak absorption between 300 and 400 nm. Given the appropriate perceptual mechanisms, these species could possess true UV-color vision and hue discrimination. Violet-specialized eyes extend into Type IIb eyes and possess violet-sensitive cone cells. UV-sensitive eyes are found throughout the fishes from at least two species of sharks to modern bony fishes. Eyes with specialized short-wavelength sensitivity are common in tropical reef fishes and must be taken into consideration when performing research involving the visual perception systems of these fishes. Because most glass and plastics are UV-opaque, great care must be taken to ensure that aquarium dividers, specimen holding containers, etc., are UV-transparent or at least to report the types of materials in use.

Anaphoric choices in Japanese fictional novels: the discourse arrangement of noun phrases, zero and third person pronouns

By examining Japanese fictional novels, this article will discuss how anaphoric devices (noun phrases (NPs), third person pronouns (TPPs), and zero anaphors) are selected and arranged in a given discourse. The traditional view of anaphora considers the co-referential relationship between anaphoric devices to be syntagmatic; that is, a pronoun, for example, refers back to its antecedent. It also declares the hierarchical order of information values between anaphoric devices; NPs are semantically the most informative, indicating an episode boundary, and pronouns less informative. Furthermore, zero anaphora is the most referentially transparent, showing the most accessibility of a topic. However, real text shows the contrary. NPs occur frequently while there is no apparent discourse boundary, and the same episode is continuous. This is because zero anaphors and TPPs (if they occur) break down readily due to the nature of a forthcoming sentence and the NP is reinstated, in order to continue the same topic in a given discourse. Therefore, the article opposes the traditional view of anaphora. Based on the concept of text processing, using ‘mental representations’, this article will determine certain occurrence patterns of the three anaphoric devices.

Direct electrochemistry of a bacterial sulfite dehydrogenase

Sulfite dehydrogenase from Starkeya novella is an alphabeta heterodimer comprising a 40.6 kDa subunit (containing the Mo cofactor) and a smaller 8.8 kDa heme c subunit. The enzyme catalyses the oxidation of sulfite to sulfate with the natural electron acceptor being cytochrome c(550). Its catalytic mechanism is thought to resemble that found in eukaryotic sulfite oxiclases. Using protein film voltammetry and redox potentiometry, we have identified both Mo- and heme-centered redox responses from the enzyme immobilized on a pyrolytic graphite working electrode: E-m,E-8 (Fe-III/II) +177 mV; E-m,E-8 (Mo-VI/V) +211 mV and E(m,)8 (Mo-V/IV) -118 mV vs NHE; Upon addition of sulfite to the electrochemical cell a steady-state voltammogram is observed and an apparent Michaelis constant (K-m) of 26(l) muM was determined for the enzyme immobilized on the working electrode surface, which is comparable with the value obtained from solution assays.

Protein film voltammetry of Rhodobacter capsulatus xanthine dehydrogenase

Xanthine dehydrogenase (XDH) from the bacterium Rhodobacter capsulatus catalyzes the hydroxylation of xanthine to uric acid with NAD(+) as the electron acceptor. R. capsulatus XDH forms an (alphabeta)(2) heterotetramer and is highly homologous to homodimeric eukaryotic XDHs. The crystal structures of bovine XDH and R. capsulatus XDH showed that the two proteins have highly similar folds; however, R. capsulatus XDH is at least 5 times more active than bovine XDH and, unlike mammalian XDH, does not undergo the conversion to the oxidase form. Here we demonstrate electrocatalytic activity of the recombinant enzyme, expressed in Escherichia coli, while immobilized on an edge plane pyrolytic graphite working electrode. Furthermore, we have determined all redox potentials of the four cofactors (Mo-VI/V, Mo-V/IV, FAD/FADH, FADH/FADH(2) and two distinct [2Fe-2S](2+/+) clusters) using a combination of potentiometric and voltammetric methods. A novel feature identified in catalytic voltammetry of XDH concerns the potential for the onset of catalysis (ca. 400 mV), which is at least 600 mV more positive than that of the highest potential cofactor. This unusual observation is explained on the basis of a pterin-associated oxidative switch during voltammetry that precedes catalysis.

Efeito da privação de sono paradoxal e do bloqueio da síntese da corticosterona sobre os limiares da reação de defesa induzida pela estimulação elétrica da matéria cinzenta periaquedutal e colículo superior

O Transtorno do pânico (TP) é um transtorno mental comum que afeta até 5% da população em algum momento da vida, sendo caracterizada pela presença de ataques de pânico (AP) recorrentes. Constitui uma psicopatologia que pode ser afetada pela privação do sono (PS), relação que ainda é pouco compreendida. Neste contexto, modelos experimentais de AP e de PS são ferramentas úteis na investigação dessa possível correlação, especialmente motivado pela crescente condição de privação de sono, que tem se tornado cada vez mais frequente na sociedade moderna. Assim, este estudo avaliou os efeitos da privação de sono paradoxal (PSP) sobre os limiares dos comportamentos defensivos induzidos por estimulação intracraniana (EI) da MCPD e CS de ratos num modelo experimental de AP, assim como verificou a influência da corticosterona sobre esses limiares. Foram utilizados 160 ratos Wistar machos (300g), organizados em 4 grupos com 40 animais cada, como se segue: Grupo Controle (CTR) submetido à EI, porém sem PSP; Grupo Privação (PRV), submetido à EI e privado por 96 horas; Grupo Privação + Bloqueio da corticosterona (PRB), submetido ao tratamento com metirapona, EI, e privado por 96 horas, e Grupo Controle + Bloqueio da corticosterona (CTB), submetido ao tratamento com metirapona e EI, porém sem privação de sono. Após 10 dias do implante cirúrgico intracraniano de eletrodo na MCPD e CS, os animais passaram por 5 sessões de estimulação, como se segue: 1ª (TRI) considerada triagem - imediatamente antes da privação, 2ª (P48) após 48h de privação, 3ª (P96) após 96h de privação, 4ª (R48) após 48h de retirada da privação e 5ª (R96) após 96h de retirada da privação. As curvas de limiares das respostas individuais de defesa obtidas nas várias sessões de estimulação da MCPD e CS (TRI, P48, P96, R48 e R96) dos ratos foram comparadas entre si, bem como as curvas de limiares de uma dada resposta nos diferentes grupos (CTR, PRV, CTB e PRB). Além disso, os níveis de corticosterona (CORT) foram dosados nas diferentes sessões de EI, e comparadas num mesmo grupo, bem como nos diferentes grupos. No grupo CTR, todos os comportamentos foram iguais em todas as sessões quando comparados à TRI, entretanto, nos animais privados (PRV), o limiar do galope (GLP) reduziu significativamente em R48 e R96, não ocorrendo xix alterações nos demais comportamentos. Em contraste, no grupo PRB, o Trote (TRT) aumentou a partir de P48, enquanto o GLP não foi alterado em nenhuma sessão de EI. Na comparação entre os grupos, em Salto (SLT), Micção (MIC), Exoftalmia (EXO), Imobilidade (IMO), Defecação (DEF), TRT e GLP, não sofreram alterações decorrentes da CORT produzida decorrente da PSP, sugerindo que a corticosterona não altera os comportamentos defensivos característicos do Ataque de Pânico. Em adição, tais resultados sugerem que os efeitos tardios da PSP sobre os limiares de GLP possivelmente se devam a mecanismos neuroquímicos tempo-dependente.

Improving fECG signal acquisition in the evaluation of fetal well-being

The ability to monitor fetal heart rate is vital during late pregnancy and labor in order to evaluate fetal well-being. Current monitoring practice is essentially based on external cardiotocography and, less frequently, during labor, invasive fetal scalp electrocardiography. Many current and envisaged applications could benefi t from simpler devices using a 3-lead ECG confi guration. We are designing a maternity support belt with an embedded wireless 3-lead ECG sensor, and have investigated the infl uence of the ground electrode position on signal quality. Data from over 100 pregnant women was collected with the ground electrode placed in 3 locations in order to determine optimum electrode placement and belt form factor.

A Wireless EEG Acquisition Platform based on Embedded Systems

This paper proposes a wireless EEG acquisition platform based on Open Multimedia Architecture Platform (OMAP) embedded system. A high-impedance active dry electrode was tested for improving the scalp- electrode interface. It was used the sigma-delta ADS1298 analog-to-digital converter, and developed a “kernelspace” character driver to manage the communications between the converter unit and the OMAP’s ARM core. The acquired EEG signal data is processed by a “userspace” application, which accesses the driver’s memory, saves the data to a SD-card and transmits them through a wireless TCP/IP-socket to a PC. The electrodes were tested through the alpha wave replacement phenomenon. The experimental results presented the expected alpha rhythm (8-13 Hz) reactiveness to the eyes opening task. The driver spends about 725 μs to acquire and store the data samples. The application takes about 244 μs to get the data from the driver and 1.4 ms to save it in the SD-card. A WiFi throughput of 12.8Mbps was measured which results in a transmission time of 5 ms for 512 kb of data. The embedded system consumes about 200 mAh when wireless off and 400 mAh when it is on. The system exhibits a reliable performance to record EEG signals and transmit them wirelessly. Besides the microcontroller-based architectures, the proposed platform demonstrates that powerful ARM processors running embedded operating systems can be programmed with real-time constrains at the kernel level in order to control hardware, while maintaining their parallel processing abilities in high level software applications.

Capital Intelectual: sua divulgação no setor bancário em Portugal

The importance of intangible resources has increased dramatically in recent years comparing to tangible ones. The economy in which we live is the result of competitive pressures that have imposed the implementation of business at an international level as well as a requirement in the application of sophisticated technologies that allow us to follow this fast evolution. In this age of information and innovation organizations will only survive if they are inserted in a global network of strategic relations, generically called as the network economy by Lev (2003). The service sector has stood out against the more traditional sectors of the economy. The intensive use of knowledge and a strong customer orientation created a new reality in today’s organizations: a growing importance attached to innovation, to the quality of products and services offered, to the information and communication technologies adopted, and to the creativity and particular abilities of human resources. The concept of intangible assets is more common in an accounting language and intellectual capital is most often applied in the context of management, being associated with a more comprehensive, multidimensional approach, representing all the knowledge that the institution owns and that it applies in the form of expertise, the creativity and organizational competencies that lead to innovation and to the sustained attainment of future economic benefits. An analysis of the scope of intellectual capital is fundamental to take more appropriate management decisions so that a more appropriate accounting treatment could be given by the accounting standardization organizations. This study intends to analyse the practices of information disclosure of the intellectual capital in the banking sector in Portugal, complementing the analysis of the disclosure of intangible assets in the context of accounting standards with the disclosure of intellectual capital in the context of organizational management. In particular, our main aims are to identify the extent of disclosure of intellectual capital made by banks in Portugal and also to identify the factors that determine such a disclosure. The disclosure in the context of accounting standards will be studied by checking the disclosure of intangible assets through the items listed in the International Accounting Standard 38 developed by the International Accounting Standards Board. The context of management was analysed by means of creating a voluntary disclosure index based on assumptions of the model Intellectus, developed by the Centro de Investigación sobre la Sociedad del Conocimiento – Instituto de Administración de Empresas (CIC-IADE) of the Universidad Autónoma of Madrid, and of the model Intellectual Capital Statement (made in Europe) (InCaS), both promoted by the European Commission and that we have adapted to the banking sector. When analysing the disclosure of intangible assets based on the context of accounting standards and the voluntary disclosure of intellectual capital, this study has tried to raise awareness about the importance of issuing reports on the intellectual capital as an alternative tool to take management decisions in the existing organizations and reflects the transparency and legitimacy that these institutions seek through a more extensive and more detailed information disclosure of their intellectual capital. Based on a complimentarily of economic theories, together with social and political theories, we tried to check the extent, evolution and tendencies of the compulsory disclosure of intangible assets and of the voluntary disclosure of the intellectual capital analysed in the period 2001-2011. Banks characteristics were also analysed in order to deduce those factors that determine or promote a larger disclosure in this sector. Based on these objectives, we adopted a longitudinal approach to explore the extent and the development of the disclosure of intangible assets as well as the factors that have determined it. Furthermore, we sought to assess the impact of the adoption of IAS 38 in the financial statements of the organizations in this sector. The disclosure index created on the basis of the disclosure requirements stated in IAS 38 from IASB was applied to the consolidated financial statements of the seventeen banks that rendered their statements in Portugal from 2001 to 2009. Since the information disclosed in the context of accounting standards may not have an important role as a management tool once it was not able to reflect what really contributes to the competitiveness and organizational growth, the voluntary disclosure of the intellectual capital was analysed according to the information obtained from the 2010 annual individual reports of the banks operating in Portugal in that year and from their respective websites in 2011. We tried to analyse the extent of the voluntary disclosure of the intellectual capital and of each of its components, human capital, structural capital and relational capital. The comparative analysis of their annual reports and their web pages allowed us to assess the incidence of the disclosure and discover what channel the banking sector focuses on when disclosing their intellectual capital. Also in this analysis the study of the disclosure determinants has allowed us to conclude about the influence of particular characteristics in the voluntary disclosure of the intellectual capital. The results of the analysis to the extent of the disclosure of intangible assets in the consolidated financial statements of the banking groups in Portugal in the period 2001-2009 have shown an average information disclosure of 0.24. This information disclosure evolved from an average value of 0.1940 in 2001 to 0.2778 in 2009. The average value is 0.8286 if it is only considered the disclosure of the intangible assets that the banks possessed. The evolution of this index means an increase in the average disclosure from 0.7852 in 2001 to 0.8788 in 2009. From the first results that are related to the extent of the disclosure of intangible assets in the financial statements, we can verify that the banking groups present a low disclosure level of these resources. However, when considering the disclosure of only the intangible assets that each institution owns, the disclosure level appears to be in compliance with the disclosure requirements for this sector. An evolution in the disclosure of intangible assets for the period considered was confirmed, showing an increase in the information disclosure of intangible assets in 2005, the year in which the accounting rules for intangible assets changed. The analysis that focused on the disclosure in the context of management tried to understand the extent, the incidence and the determinants of the voluntary information disclosure of intellectual capital in the annual reports of 2010 and on their web pages in 2011, studying the 32 banks operating in Portugal in this period. The average voluntary disclosure of the intellectual capital in the 2010 annual reports is 0.4342 while that in web pages is 0.2907. A review of the components of the intellectual capital allowed us to assess the importance that the banks confer to each of these components. The data obtained show that the relational capital, and more specifically the business capital, is the most disclosed component by banks in Portugal both in the annual reports and in their institutional web pages, followed by the structural capital and, finally, by the human capital. The disclosure of the human capital and the structural capital is higher in the annual reports than that in the websites, while the relational capital is more disclosed in the websites than in the annual reports. The results have also shown that the banks make a complementary use of both sources when disclosing information about their structural capital and relational capital but they do not show any information about their human capital in their websites. We tried to prove the influence of factors that could determine the accounting disclosure and the voluntary disclosure of the intellectual capital in this sector. The change in the IASB accounting rules as from January 1st 2005 gave a greater disclosure of accounting information of intangible assets in the financial statements of banks. The bank size and corporate governance measures have statistically proved to have an influence on the extent of the accounting disclosure of intangible assets and on the voluntary disclosure of the intellectual capital. Economic and financial variables such as profitability, operating efficiency or solvency were not determinants of information disclosure. The instability that the banking sector has experienced in economic and financial indicators in recent years as a result of the global financial markets imbalance has worsen indicators such as profitability, efficiency and solvency and caused major discrepancies in the economic situation between banks in Portugal. This empirical analysis has contributed to confront the disclosure required by accounting rules performed in the financial statements of organizations with that performed in the main disclosure media which is available for entities and which is increasingly requested in the process of taking management decisions. It also allowed us to verify whether there is homogeneity between institutions in the fulfilment of the requirements for information disclosure of intangible assets. However, as for voluntary disclosure of intellectual capital, there are large disparities in the disclosure extent between organizations. Regardless of this sector specific characteristics, the voluntary disclosure of intellectual capital made by banks in Portugal follows the trends in other sectors and the practices adopted in other countries, namely regarding the amount of information disclosed, the incidence of the disclosure on the indicators of relational capital and the importance of variables such as size as determinants of disclosure of intellectual capital. For a further knowledge in this field, we created a specific index for the banking sector, considering appropriate indicators for an incisive, comprehensive analysis in order to consider the most relevant indicators of intellectual capital components. Besides, confronting the analysis of disclosure in the context of accounting standards with the study of voluntary disclosure brought a new analysis approach to the research on intellectual capital disclosure. With this study, we have also intended to raise greater awareness of the need for harmonization in the intellectual capital disclosure on the part of the regulatory banking authority by means of a demanding, consistent and transparent report of intellectual capital with simple, clear, objective indicators so that those interested in disclosing intellectual capital information in the organizations in this sector may obtain more harmonized and comparable information. A research on the disclosure quality of intellectual capital, together with the application of other analysis methodologies in this sector, might be a promising approach for future research. Applying the voluntary disclosure index to the same sector in other countries may also contribute to the knowledge of disclosure practices in different geographical environments. We highlight the relevance of further studies contributing to the harmonization and consistency in the presentation of an intellectual capital report so as to enable organizations to disclose the resources that contribute most to their competitiveness and growth.

The determinants of international equity investment: Do they differ between institutional and noninstitutional investors?

In this paper we investigate whether the determinants of international equity investment differ between investors with different degrees of sophistication. For this purpose, we analyse and compare the determinants of international equity investment of institutional and noninstitutional investors from 20 OECD countries (US not included) in the period 2001-2009. The results show that there are significant differences in the determinants of international equity investment between institutional and noninstitutional investors. In particular, noninstitutional investors tend to exhibit a more pronounced preference for equities of geographical nearby, contiguous and more transparent countries than institutional investors. The preference for more developed equity markets and the contrarian behaviour are also significantly more pronounced for noninstitutional than for institutional investors. These results support the argument that international equity investment of less sophisticated investors is more affected by information costs and familiarity than that of more sophisticated investors. Moreover, business cycles exert an influence on international equity investment decisions of both institutional and noninstitutional investors.

The determinants of international equity and bond investment

The purpose of this research is fourfold. First, to investigate whether the determinants of international equity investment differ between investors with different degrees of information, experience and sophistication. For this purpose, the determinants of international equity investment of institutional and noninstitutional investors from 20 OECD countries, in the period 2001-2009, were analysed and compared. The results show that there are significant differences in the determinants of international equity investment between institutional and noninstitutional investors. Particularly, noninstitutional investors exhibit a more pronounced preference for equities of geographical nearby, contiguous and more transparent countries than institutional investors, suggesting that the effect of information costs and familiarity on international equity investment is stronger for less informed, experienced and sophisticated investors. Moreover, the preference for more developed equity markets and the contrarian behaviour are more severe for noninstitutional investors. Hence, the heterogeneity of institutional and noninstitutional investors in international equity investment is not negligible and therefore should be taken into account. Second, to investigate whether the determinants of international bond investment differ between investors with different degrees of information, experience and sophistication. For this purpose, the determinants of international bond investment of institutional and noninstitutional investors from 20 OECD countries, in the period 2001-2009, were analysed and compared. The results show that there are few significant differences in the determinants of international bond investment between institutional and noninstitutional investors. Particularly, the preference for bonds of more transparent countries and the return chasing behaviour are more pronounced for noninstitutional investors, whereas the preference for bonds with lower risk diversification potential is more pronounced for institutional investors. Hence, not only the results for international bond investment do not allow to support (or reject) the argument that information costs and familiarity are more important for less informed, experienced and sophisticated investors, but also they are contrary to the idea that financial variables, namely return and risk diversification, are more important for more informed, experienced and sophisticated investors. Third, to investigate whether the determinants of international equity investment differ from the determinants of international bond investment. For this purpose, the determinants of both international equity and bond investment of institutional and noninstitutional investors from 20 OECD countries, in the period 2001-2009, were analysed and compared. The results show that, although the effect of information costs on international equity investment tends to be stronger than on international bond investment, the differences between assets are not usually statistically significant, especially when the influence of financial variables is taken into account. Hence, it is not possible to conclude that international equity investment is much more information intensive than international bond investment, as suggested by Gehrig (1993) and Portes, Rey and Oh (2001), among others. Fourth, to investigate whether the flight to quality phenomenon is also observable in international investment and whether the flight to quality phenomenon is more pronounced for more sophisticated than for less sophisticated investors. For this purpose, a two-factor and three-factor ANOVA models, respectively, were applied to the international equity and bond investment of institutional and noninstitutional investors from 20 OECD countries in the period 2001-2009. The results suggest that the flight to quality phenomenon is also observable in international investment, as a change from business cycle of expansion to recession causes investors to significantly decrease the average weight invested in more risky assets (equities) and increase the average weight invested in less risky assets (bonds). The results also show that the variation on the average weight assigned to each type of asset, due to changes in business cycles, is significantly stronger for institutional investors than for noninstitutional investors, thereby suggesting that the flight to quality phenomenon is more pronounced for more sophisticated than for less sophisticated investors.

A systematic procedure to enhance reproducibility of SWASV cycles in the determination of toxic metals in real samples

This work presents for the first time a systematic study on the optimization of the electrochemical cleaning time of a mercury film when it is used as a working electrode material in the analysis of toxic metals, such as Pb2+, used as model metal, in real samples by SWASV. The optimization study for the film’s cleaning time aimed at attaining a Pb2+ minimum value in the film after the re-oxidation step of the pre-concentrated metal, given the impossibility of complete removal of traces of the electroactive species from the film. This value was kept constant in each concentration range studied ensuring thus that all assays were performed in initial identical conditions. An assay performed on a synthetic sample was taken as reference. In it, given the absence of matrix effects, and after the electrochemical cleaning step, a direct proportionality was observed between the residual amounts of Pb2+ in the film (which for the cleaning time used was never completely removed) and Pb2+ concentration in the solution. This fact determined a high correlation between Pb2+ peak current and Pb2+ concentration which was not observed when real samples (tree leaves) were analyzed. This behavior may result from the presence of the interfering surfactants always present in real samples of complex matrix. Cleaning time optimization was performed for the following Pb2+ concentration ranges in the real samples of complex matrix: 0.006-0.020, 0.020-0.080, 0.060-0.200 and 0.100-0.600 ppb. As expected, in order to obtain identical levels of film’s cleaning efficiency, the need for longer cleaning times has been observed for higher concentrations. The optimized cleaning times for the concentration ranges under study were 120, 150, 180 e 300 s, respectively.

Field effect and light-assisted a-Si:H sensors for detection of ions in solution

In this paper we present an amorphous silicon device that can be used in two operation modes to measure the concentration of ions in solution. While crystalline devices present a higher sensitivity, their amorphous counterpart present a much lower fabrication cost, thus enabling the production of cheap disposable sensors for use, for example, in the food industry. The devices were fabricated on glass substrates by the PECVD technique in the top gate configuration, where the metallic gate is replaced by an electrolytic solution with an immersed Ag/AgCl reference electrode. Silicon nitride is used as gate dielectric enhancing the sensitivity and passivation layer used to avoid leakage and electrochemical reactions. In this article we report on the semiconductor unit, showing that the device can be operated in a light-assisted mode, where changes in the pH produce changes on the measured ac photocurrent. In alternative the device can be operated as a conventional ion selective field effect device where changes in the pH induce changes in the transistor's threshold voltage.